A video posted by Ken Martin, of Boston, shows the moments just after the shark attacked the seal. Lifeguards can be seen ushering the last few surfers inland, while a separate video posted by Martin shows the bloody carcass of a seal floating in the water. The latter had nearly 100,000 views as of Wednesday afternoon.

The shark allegedly “took out a seal in the middle of 20 surfers” just 30 feet from the shore, Martin described onTwitter, adding in a separate tweet that the shark disappeared shortly after the event.

Martin said “chaos” ensued for a few minutes after the attack until everyone at the beach was accounted for.

“My daughter had a seal swim up on her about 10 days ago exact sandbar and had no idea until people in the beach started to yell to her to move. Have to avoid the seals and all should be ok,” Martin advised one Twitter user.